I've been doing a lot of digging regarding the Cobb/jb4 question with our is'.
One important factor to consider is if you have DCT vs. 6mt
If you have a manual, get a jb4 and call it a day. You may eventually need a back end flash as well depending on how deep in the tuning pool you swim.
If you have DCT, it is highly advisable to start with a flash, like Cobb. There can be potential problems because a piggy tricks the dme into doing things it wants. Unfortunately, this also fools information that helps control the DCT. Line pressure for example. This can cause slippage and wear and tear on your expensive transmission.
A flash tune like Cobb sends accurate information to the DCT so it can behave accordingly.
Ultimately however, there are lots of cool features on the jb4 that you can't necessarily get on a flash tune. So, get both! Bms has special maps for the iS that can be installed with a Cobb (or oft for that matter) that support the jb4 and will be much better for your DCT.
I started with a Cobb. Mainly because I am still under warranty + maintenance package so I have frequent trips to the dealer ahead of me. So it's nice to not have to pull the jb4 every time.
But I have decided to stack it with the jb4 eventually, probably after my next oil change and brake service.
That's my .02

I've been doing a lot of digging regarding the Cobb/jb4 question with our is'.
One important factor to consider is if you have DCT vs. 6mt
If you have a manual, get a jb4 and call it a day. You may eventually need a back end flash as well depending on how deep in the tuning pool you swim.
If you have DCT, it is highly advisable to start with a flash, like Cobb. There can be potential problems because a piggy tricks the dme into doing things it wants. Unfortunately, this also fools information that helps control the DCT. Line pressure for example. This can cause slippage and wear and tear on your expensive transmission.
A flash tune like Cobb sends accurate information to the DCT so it can behave accordingly.
Ultimately however, there are lots of cool features on the jb4 that you can't necessarily get on a flash tune. So, get both! Bms has special maps for the iS that can be installed with a Cobb (or oft for that matter) that support the jb4 and will be much better for your DCT.
I started with a Cobb. Mainly because I am still under warranty + maintenance package so I have frequent trips to the dealer ahead of me. So it's nice to not have to pull the jb4 every time.
But I have decided to stack it with the jb4 eventually, probably after my next oil change and brake service.
That's my .02

You pretty much just confirmed all of my research. thanks for your input i was leaning a little more towards the COBB bc i didnt want to start with gobs of power and not understand the tuning process. where as i feel cobb has a bigger support network and there are more people who are a little more responsible when it comes to managing the power of their car. I want to get the JB4 and stack it like you but first im getting a protune and then ill see from there. WE ALL WANT MORE POWER. I think it will be better to go this route and learn some about both.

The thing about the protune is it is specific for the mods and gas you have at that moment. So if you intend on doing regular upgrades for a while I would hold off and stick to the OTS maps for a while until your done adding bolt-ons. Besides, for the price of a protune, your not too far off from the jb4 which is much more easily adapted to whatever mods/fuel you have at the moment.
Also, I read somewhere recently that terry at BMS is working on some DCT specific perks like changing launch control rpms or having the sport button default on. Just more reasons to go with a stack.

I was running JB4 on a bone stock 2013 335is with DCT. I went from an "integrated" unit to ISO running 16.hex to 24.hex every increment along the way. I had the best success with 18B.hex

Once you mod your car with DCI, DP, FMIC, bigger turbos and new exhaust, you really need something like the JB4 or Cobb or Proceed to compensate for the changes you have made. But for the 335is, BMW has already made some of those changes for you. I had nothing but problems since day one - guinea pigging myself on a daily basis. Since I remained stock, the JB4 didn't really help much. In the end, the JB4 wasn't able to clear the codes faster than the ECU was able to create them.

I was running JB4 on a bone stock 2013 335is with DCT. I went from an "integrated" unit to ISO running 16.hex to 24.hex every increment along the way. I had the best success with 18B.hex

Once you mod your car with DCI, DP, FMIC, bigger turbos and new exhaust, you really need something like the JB4 or Cobb or Proceed to compensate for the changes you have made. But for the 335is, BMW has already made some of those changes for you. I had nothing but problems since day one - guinea pigging myself on a daily basis. Since I remained stock, the JB4 didn't really help much. In the end, the JB4 wasn't able to clear the codes faster than the ECU was able to create them.

The thing about the protune is it is specific for the mods and gas you have at that moment. So if you intend on doing regular upgrades for a while I would hold off and stick to the OTS maps for a while until your done adding bolt-ons. Besides, for the price of a protune, your not too far off from the jb4 which is much more easily adapted to whatever mods/fuel you have at the moment.
Also, I read somewhere recently that terry at BMS is working on some DCT specific perks like changing launch control rpms or having the sport button default on. Just more reasons to go with a stack.

I will indeed get a protune after im done doing the mods. Right now Im overseas so im just buying all of my mods now and when i get home in a couple months itll all be waiting for me. then go get the protune lol easy as that!

I have a 2013 335is coupe. Did a s2 dinan performance upgrade. Just put on the Free Flow Exhaust with black tips. The sound of the cold start up is amazing because its a deep put (similar to the sound of a v8). However driving, barely hear it. I think I got spoiled with the fine tune of the stock exhaust. On the other hand, the car does perform much better.

I have a 2013 335is coupe. Did a s2 dinan performance upgrade. Just put on the Free Flow Exhaust with black tips. The sound of the cold start up is amazing because its a deep put (similar to the sound of a v8). However driving, barely hear it. I think I got spoiled with the fine tune of the stock exhaust. On the other hand, the car does perform much better.

Any ideas to make it louder?

Catless DP's and if that's not good enough then second resonators delete and maybe increase size of exhaust piping to 2.5 - 2.75.

I was running JB4 on a bone stock 2013 335is with DCT. I went from an "integrated" unit to ISO running 16.hex to 24.hex every increment along the way. I had the best success with 18B.hex

Once you mod your car with DCI, DP, FMIC, bigger turbos and new exhaust, you really need something like the JB4 or Cobb or Proceed to compensate for the changes you have made. But for the 335is, BMW has already made some of those changes for you. I had nothing but problems since day one - guinea pigging myself on a daily basis. Since I remained stock, the JB4 didn't really help much. In the end, the JB4 wasn't able to clear the codes faster than the ECU was able to create them.

Whatever...I still stick by my original impression back in April 2013:

Interesting. My experience has been the opposite. Car functions flawlessly but I'm running the latest hex updates. Very interested in dynoing on a couple different maps to have some hard data as well as some dragstrip time.